1. Field of the Invention
The present invention relates to an electrostatic discharge protection component (hereinafter referred to simply as protection component) which protects an electronic device from electrostatic discharge.
2. Background Art
In recent years, electronic devices such as mobile phones are rapidly reducing in size and increasing in function. Along with this trend, their circuits are becoming denser, and on the other hand, are having lower and lower withstand voltages. As a result, when a person happens to come into contact with a circuit terminal of an electronic device, an electrostatic discharge pulse that is caused by the contact more and more tends to damage an electric circuit in the device, thereby causing an increasing number of defects.
A conventional countermeasure against such electrostatic discharge pulses is to provide a multilayer chip varistor between the incoming line of electrostatic discharge and the ground so as to bypass the electrostatic discharge, thereby reducing the voltage applied to the circuit of the electronic device.
An example of conventional multilayer chip varistors to suppress electrostatic discharge is disclosed in Japanese Patent Unexamined Publication No.H08-31616.
However, as they are becoming smaller and more functional, electronic devices have an increasing number of parts to be protected against electrostatic discharge pulses. On the other hand, there is a growing demand for protection components of an array type having a plurality of components, as well as of a single component type. Also, in order to achieve smaller and thinner electronic devices, protection components are expected to be thinner.
It is difficult, however, to thin the conventional multilayer chip varistors because they must have a specific thickness in order to keep the physical strength of their material. For example, a commercially available multilayer chip varistor with a width of 1.25 mm and a length of 2.0 mm or so must have a thickness of not less than 0.5 mm. If it is desired to further reduce the thickness, the varistor is required to be further decreased in size. This makes it very difficult to integrate a number of components into an array. Thus, in the case of a multilayer chip varistor, its thickness and the number of components in the array have a trade-off relation with each other.
The cause of the trade-off relation is the low flexural strength of a zinc oxide-based material contained in the multilayer chip varistor. More specifically, using this material for a chip component makes the flexural strength as low as 100 MPa or lower. This low flexural strength makes it difficult to avoid the trade-off relation in the conventional multilayer chip varistors.
The present invention has an object of providing a protection component of an array type which has a low-profile, a large mechanical strength and excellent practicality.